number of turns question

[klsmurf]

Hi all,

 I'm working on a small dual rotor axial using mainly reclaimed parts. I knew I was going to be real close with the wire available. 12 coils, 2-in-hand, #21, 74 turns.
10 coils came out fine, the next one I was only able to get 72 with what I had left. The 12th coil will be rewound from a previously made larger coil.

The questions/options

1. Do I just leave the one coil short on turns? It's just a hobby mill after all.
2. Do I wind the final coil with 2 extra turns and make sure it is in the same phase set of coils?
3. Wind the last coil with 72 and remove 2 turns from the other 10?

I like 1 or 2.

On an unrelated topic, what writing format can be copied and pasted to the board? ie. word,notepad, word pad, others?

Thanks Kevin

[Flux]

Interesting problem.

1.   leaving one coil 2 turns short will make virtually no difference, it will unbalance the 3 phase output but for this duty that may not be a bad thing, some manufacturers have used that approach to get a better track to the cube law.

2.  If you have the space to do that then it keeps the windings balanced and gets you back to the design intention.

3.. That will raise your cut in speed, which may be a disadvantage or it may help depending on your wind area and how well you match your prop. Anyway 2 turns in 74 will make so little difference that you probably won't spot the difference.

Take your pick, all 3 options will work fine, unless you try all 3 methods you will never know which was best and it would take some pretty accurate measurements to decide even then.

Flux

[klsmurf]

Thank you Flux for the answers.

 I figured for what I'm doing, it wasn't going to be a big problem, no matter which choice I went with. It's nice to get it confirmed as electricity and myself are only acquaintances.

[hiker]

no sweat 2  turns........so what size of rotors are you using-mags.?

[dave ames]

Hey Kevin,

Would love to see and hear more about your project..There's something about following along on a build that stirs the inner tinkerer 

It's all good fun!
Cheers, dave

[klsmurf]

Hey Hiker,
I went ahead and added 2 turns to the final coil, I had the room.
The rotors are 7.5" and I'm using HDD mags.

Hey Dave,
Tinkerin' and learnin', not much better!   I'm contemplating doing a diary even though it's just a small hobby mill.

Kevin

[jlt]

are u using the whole hhdrive mags or are they cut in half.

[klsmurf]

Hey there jlt,

I use halves. Gloves, glasses and a pair of tile nippers does the trick.

Kevin